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Creating Essential Files and Symlinks
/etc/passwd
/etc/group
/run/utmp
/var/log/btmp
/var/log/lastlog
/var/log/wtmp
Historically, Linux maintained a list of the mounted file systems in the file <filename>/etc/mtab</filename>. Modern kernels maintain this list internally and expose it to the user via the <filename class="directory">/proc</filename> filesystem. To satisfy utilities that expect to find <filename>/etc/mtab</filename>, create the following symbolic link:
<userinput>ln -sv /proc/self/mounts /etc/mtab</userinput>
Create a basic <filename>/etc/hosts</filename> file to be referenced in some test suites, and in one of Perl's configuration files as well:
<userinput>cat &gt; /etc/hosts &lt;&lt; EOF
<literal>127.0.0.1 localhost $(hostname)
::1 localhost</literal>
EOF</userinput>
In order for user <systemitem class="username">root</systemitem> to be able to login and for the name <quote>root</quote> to be recognized, there must be relevant entries in the <filename>/etc/passwd</filename> and <filename>/etc/group</filename> files.
Create the <filename>/etc/passwd</filename> file by running the following command:
<userinput>cat &gt; /etc/passwd &lt;&lt; "EOF"
<literal>root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/dev/null:/usr/bin/false
daemon:x:6:6:Daemon User:/dev/null:/usr/bin/false
messagebus:x:18:18:D-Bus Message Daemon User:/run/dbus:/usr/bin/false
uuidd:x:80:80:UUID Generation Daemon User:/dev/null:/usr/bin/false
nobody:x:65534:65534:Unprivileged User:/dev/null:/usr/bin/false</literal>
EOF</userinput>
<userinput>cat &gt; /etc/passwd &lt;&lt; "EOF"
<literal>root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/dev/null:/usr/bin/false
daemon:x:6:6:Daemon User:/dev/null:/usr/bin/false
messagebus:x:18:18:D-Bus Message Daemon User:/run/dbus:/usr/bin/false
systemd-journal-gateway:x:73:73:systemd Journal Gateway:/:/usr/bin/false
systemd-journal-remote:x:74:74:systemd Journal Remote:/:/usr/bin/false
systemd-journal-upload:x:75:75:systemd Journal Upload:/:/usr/bin/false
systemd-network:x:76:76:systemd Network Management:/:/usr/bin/false
systemd-resolve:x:77:77:systemd Resolver:/:/usr/bin/false
systemd-timesync:x:78:78:systemd Time Synchronization:/:/usr/bin/false
systemd-coredump:x:79:79:systemd Core Dumper:/:/usr/bin/false
uuidd:x:80:80:UUID Generation Daemon User:/dev/null:/usr/bin/false
systemd-oom:x:81:81:systemd Out Of Memory Daemon:/:/usr/bin/false
nobody:x:65534:65534:Unprivileged User:/dev/null:/usr/bin/false</literal>
EOF</userinput>
The actual password for <systemitem class="username">root</systemitem> will be set later.
Create the <filename>/etc/group</filename> file by running the following command:
<userinput>cat &gt; /etc/group &lt;&lt; "EOF"
<literal>root:x:0:
bin:x:1:daemon
sys:x:2:
kmem:x:3:
tape:x:4:
tty:x:5:
daemon:x:6:
floppy:x:7:
disk:x:8:
lp:x:9:
dialout:x:10:
audio:x:11:
video:x:12:
utmp:x:13:
usb:x:14:
cdrom:x:15:
adm:x:16:
messagebus:x:18:
input:x:24:
mail:x:34:
kvm:x:61:
uuidd:x:80:
wheel:x:97:
users:x:999:
nogroup:x:65534:</literal>
EOF</userinput>
<userinput>cat &gt; /etc/group &lt;&lt; "EOF"
<literal>root:x:0:
bin:x:1:daemon
sys:x:2:
kmem:x:3:
tape:x:4:
tty:x:5:
daemon:x:6:
floppy:x:7:
disk:x:8:
lp:x:9:
dialout:x:10:
audio:x:11:
video:x:12:
utmp:x:13:
usb:x:14:
cdrom:x:15:
adm:x:16:
messagebus:x:18:
systemd-journal:x:23:
input:x:24:
mail:x:34:
kvm:x:61:
systemd-journal-gateway:x:73:
systemd-journal-remote:x:74:
systemd-journal-upload:x:75:
systemd-network:x:76:
systemd-resolve:x:77:
systemd-timesync:x:78:
systemd-coredump:x:79:
uuidd:x:80:
systemd-oom:x:81:
wheel:x:97:
users:x:999:
nogroup:x:65534:</literal>
EOF</userinput>
The created groups are not part of any standard&mdash;they are groups decided on in part by the requirements of the Udev configuration in Chapter 9, and in part by common conventions employed by a number of existing Linux distributions. In addition, some test suites rely on specific users or groups. The Linux Standard Base (LSB, available at <ulink url="https://refspecs.linuxfoundation.org/lsb.shtml"/>) only recommends that, besides the group <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0, a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be present. The GID of 5 is widely used for the <systemitem class="groupname">tty</systemitem> group, and the number 5 is also used in <phrase revision="systemd">systemd</phrase> <phrase revision="sysv"><filename>/etc/fstab</filename></phrase> for the <systemitem class="filesystem">devpts</systemitem> filesystem. All other group names and GIDs can be chosen freely by the system administrator since well-written programs do not depend on GID numbers, but rather use the group's name.
The ID 65534 is used by the kernel for NFS and separate user namespaces for unmapped users and groups (those exist on the NFS server or the parent user namespace, but <quote>do not exist</quote> on the local machine or in the separate namespace). We assign <systemitem class="username">nobody</systemitem> and <systemitem class="groupname">nogroup</systemitem> to avoid an unnamed ID. But other distros may treat this ID differently, so any portable program should not depend on this assignment.
Some tests in <xref linkend="chapter-building-system"/> need a regular user. We add this user here and delete this account at the end of that chapter.
<userinput>echo "tester:x:101:101::/home/tester:/bin/bash" &gt;&gt; /etc/passwd
echo "tester:x:101:" &gt;&gt; /etc/group
install -o tester -d /home/tester</userinput>
To remove the <quote>I have no name!</quote> prompt, start a new shell. Since the <filename>/etc/passwd</filename> and <filename>/etc/group</filename> files have been created, user name and group name resolution will now work:
<userinput>exec /usr/bin/bash --login</userinput>
The <command>login</command>, <command>agetty</command>, and <command>init</command> programs (and others) use a number of log files to record information such as who was logged into the system and when. However, these programs will not write to the log files if they do not already exist. Initialize the log files and give them proper permissions:

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  1. Linux From Scratch 11.3
  2. chapter07_createfiles
  3. English
<userinput>cat &gt; /etc/hosts &lt;&lt; EOF
<literal>127.0.0.1 localhost $(hostname)
::1 localhost</literal>
EOF</userinput>
a year ago
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String information

Source string description
type: Content of: <sect1><screen>
Flags
ignore-same, no-wrap, read-only
Source string location
lfs-en/chapter07/createfiles.xml:50
String age
a year ago
Last updated
9 months ago
Source string age
a year ago
Translation file
string 11